Wednesday, July 8, 1998 Last modified at 12:50 a.m. on Wednesday, July 8, 1998

Women smoke as they converse outside a downtown Chicago office building Tuesday, July 7, 1998. The Journal of the American Medical Association reports in the Wednesday, July 8, 1998, edition that according to two new studies, blacks absorb more nicotine per cigarette than other races, suggesting they may be more vulnerable to nicotine addiction. AP PhotoScientists study race, nicotine

CHICAGO (AP) - Blacks seem to absorb more nicotine per cigarette than smokers of other races, a finding that could explain why they run a higher risk of lung cancer and have more trouble kicking the habit, researchers say.

Why blacks seem to get more nicotine from cigarettes isn't clear. Researchers said there is disagreement over whether it results from biological differences in how blacks and whites process nicotine, differences in smoking habits between the races, or both.

The findings are contained in two studies published in Wednesday's Journal of the American Medical Association.

One study, led by Ralph S. Caraballo of the Centers for Disease Control and Prevention, measured blood levels of a chemical called cotinine, a byproduct of the breakdown of nicotine in the body, in a nationally representative sample of U.S. adult smokers from 1988 to 1991.

Cotinine was measured instead of nicotine because it stays in the body much longer and scientists have developed a highly sensitive test for it.

Black smokers had cotinine concentrations substantially higher at all levels of cigarette smoking than white smokers did, the researchers said, after taking into account differences that could skew

the results, such as weight, number of other smokers in the home and smoke exposure at work.

Previous research indicates black smokers are more likely to try quitting and have a lower success rate than white smokers. Also, black smokers run a higher risk of developing lung cancer and dying from it.

Higher nicotine absorption could help explain the lower quitting rate among blacks, the researchers said.

Also, if blacks have higher cotinine levels because they inhale more deeply or smoke stronger cigarettes, they also would take in more cancercausing substances such as tar. That, in turn, may explain why black smokers get lung cancer at higher rates than white smokers, the researchers said.

In a related study, a separate team of researchers compared rates of metabolism - the body's process of breaking down food to make energy - and nicotine intake among 40 black and 39 white smokers.

Cotinine blood levels per cigarette smoked were significantly higher in black smokers than in white smokers, said the researchers, led by Dr. Eliseo J. Perez-Stable of the University of California at San Francisco.

Although no significant difference was found in rates of nicotine metabolism, blacks cleared cotinine from their bodies at slower rates and took in more nicotine per cigarette.

Dr. Edward M. Sellers, a professor of pharmacology and medicine at the University of Toronto and Women's College Hospital, said that doesn't mean differences in nicotine metabolism between races don't exist. Instead, the study may have been too small to show such differences, said Sellers, who was not involved in either study.

Differences in nicotine metabolism could be important: A person whose body uses up nicotine relatively fast might, as a result, crave more cigarettes, inhale more deeply or choose a stronger brand.

Sellers praised both studies as careful and important but agreed with their authors that more research is needed.

He said it is well-established that blacks metabolize some drugs differently because of genetic differences. And recent studies suggest a genetic trait linked to protection from nicotine addiction may be missing in Africans, he said.

He said he believes genetic differences will probably account for differing smoking patterns among the races.

"If you can understand the genetic basis for the addictive disorder," he said, "then you might be able to actually individualize treatment, not only by group, but by an individual's genetic characteristics."